Print PageIt is generally thought that the first non-aquatic ecosystems on Earth started with the advent of plants in the early Phanerozoic (< 542 Ma). This idea largely derives from our poor understanding of older continental deposits and their oftentimes paleoenvironmental misinterpretation, along with the apparent lack of fossils and ichnofossils in them. Today, we know that microbes, already abundant by ~3500 Ma ago, were adapted to live in subaerial conditions in peritidal and in-land, pre-Phanerozoic environments, for which we have a record of sedimentary biostructures, organic compounds, and microfossils, in rocks as old as 2700 Ma. Yet, this evidence is so rare in comparison with that from aquatic environments, that the concept of microbial communities forming the earliest land ecosystems has not been fully integrated into our general knowledge.
Results/Conclusions
The rapid adaptations we see in modern microbes, their high tolerance to environmental fluctuations (e.g. desiccation and salinity), their early appearance in the fossil record, and the evidence of colonization of coastal environments since 3400 Ma, favors that the dry lands could have been colonized by microbes as well. Presently, Biological soil crusts (BSC) are the most abundant microbial ecosystems in plant-less land surfaces, and have been considered analogs of ancient ‘soil’ communities. However, recognizing the presence of a microbial cover on ancient land deposits is not trivial. In this talk, I will review the extant evidence of land microbial communities throughout time, and will show a variety of morphological traits exhibited by modern BSCs, which can be used as biosignatures for their identification in the rock record. A better understanding on the ‘signatures’ left behind by microbes in the recent seems crucial for their recognition in Phanerozoic and pre-Phanerozoic rocks.
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